A Selective Metal-Mediated Approach for the Efficient Self-Assembling of Multi-Component Photoactive Systems

We report on the efficient use of different coordinative affin- ities to quantitatively construct a three-component multi- chromophore system containing one free-base porphyrin, one aluminium(III) monopyridylporphyrin, and one ruth- enium(II) tetraphenylporphyrin in a single step. The Al III monopyridylporphyrin plays the pivotal role in directing the correct self-assembly process, and it behaves as the antenna unit for the photoinduced processes of interest. A two-com- ponent system, containing the same free-base porphyrin and one aluminium(III) tetraphenylporphyrin, was prepared for comparative studies. Both systems are remarkably stable in chlorinated solutions. Their photophysical behaviour was studied in detail by stationary and time-resolved emission techniques. In the two-component system, fast and efficient singlet energy transfer from the Al–porphyrin to the free- base porphyrin is observed; in the three-component system, upon excitation of the Al–porphyrin, a fast (minor of 250 ps) electron transfer process from the Ru–porphyrin to the aluminium–porphyrin is observed.